In general, data processors communicate with all of the different types of system resources using the same communication bus. For example, the data processor would communicate with both the primary and the secondary memories using the same communication bus. Similarly, the same communication bus would be used to communicate with input/output controllers and the like. If communication is necessary in a particular system with a resource which is unable to utilize the existing common communication bus because of data port size incompatibility, an interface adapter must be employed to buffer data transfers between the processor's bus and that of the resource. In addition to adding additional circuitry to the system, the interface devices require that the data processor provide specific directions for each such transfer.